The present invention relates to a liquid jetting device provided with main and sub tanks for supplying liquid to a liquid jetting head, and a liquid supplying method in use for the liquid jetting device.
An ink jet recording device is known as one form of the liquid jetting device. The ink jet recording device includes a liquid jetting head and a paper feeder. Generally, the liquid jetting head is mounted on a carriage, and moved in the width direction of a recording paper as a target, and jets ink droplets as liquid droplets onto the recording paper. The paper feeder relatively moves the recording paper in the direction perpendicular to the moving direction of the liquid jetting head.
In the ink jet recording device, something is printed on the recording paper in a manner that the liquid jetting head ejects, ink droplets on the recording paper in accordance with print data as jetting data.
The ink jet recording device is capable of a full color printing as well as the text printing by use of black ink. To the full color printing, liquid jetting heads capable of jetting or ejecting color inks of, for example, black, yellow, cyan and magenta are mounted on the carriage, and ink ejection ratios of those inks are varied.
Ink cartridges as liquid cartridges for supplying the inks to the liquid jetting heads are disposed within the ink jet recording device.
In a normal ink jet recording device, ink cartridges containing the inks are mounted on the carriage, and moved together with the carriage.
In the ink jet recording device, which are supplied for office or business use, ink cartridges of large capacity are located outside the carriage for dealing with the printing of a relatively large volume of data.
An ink jet recording device of the type in which an ink cartridge holder provided in the apparatus main body is loaded with a main tank as an ink cartridge, is also known. Sub tanks are provided on the cartridge on which the liquid jetting heads are mounted. Ink is supplied from each main tank to a related sub tank through an ink supplying tube (ink passage) as a liquid supplying tube. Further, the ink is supplied from the sub tank to a related liquid jetting head.
To improve the throughput, such a recording device is required to have such a function that ink is successively supplied from each main tank to the related sub tank while the printing is executed, and the ink is stably supplied from the sub tank to the related liquid jetting head.
To satisfy such a requirement, preferably employed, is that an ink pack as a liquid pack in the main tank is pressurized by air to cause an ink stream flowing from the main tank to the sub tank, thereby enabling the supplying ink to the sub tank. In this case, it is important that an excessive pressure is not applied to the ink pack of the main tank.
To avoid the excessive pressure application, an ink jet recording device with a liquid supplying system as shown in FIG. 5 has been used. In the device, a pressure of ink is adjusted when it is supplied from the main tank to the sub tank.
The ink supplying system of the ink jet recording device will be described with reference to FIG. 5.
In the figure, reference numeral 21 designates an air pressure pump. Air that is pressurized by the air pressure pump 21 is supplied to a pressure regulating valve 22, and is supplied to main tanks 9 (only one main tank is illustrated) by way of a pressure detector 23.
The pressure regulating valve 22 operates such that when air that is pressurized by the air pressure pump 21 reaches a predetermined pressure or higher, the valve is opened to regulate the pressure of the air applied to the main tanks 9 to be within a predetermined range of pressure. The pressure detector 23 detects a pressure of the air pressurized by the air pressure pump 21, and controls the driving of the air pressure pump 21.
With such an arrangement, each main tanks 9 (ink pack 24) receives the pressure of the pressurized air, and creates an ink stream from the main tank 9 to the related sub tank under the predetermined pneumatic pressure.
The ink pressurized by each main tank 9 is supplied to a related sub tank by a related ink supplying valve 26 and a related ink supplying tube 10.
In the liquid jetting device thus arranged, the pneumatic pressure that is supplied from the air pressure pump 21 to the main tank 9 is regulated, by use of the pressure regulating valve 22 and the pressure detector 23, in the following way.
When the pressure detector 23 detects that a pressure of the air pressurized by the air pressure pump 21 reaches a predetermined pressure, the air pressure pump 21 is stopped. When the pressure detector 23 detects that a pressure of the air pressurized by the air pressure pump 21 decreases to be below the predetermined pressure, the air pressure pump 21 is driven.
The liquid jetting device, which employs such a pneumatic pressure regulating arrangement, has disadvantages of increase of the number of required parts, complicated control for the pressure regulation, and increase of cost to manufacture.
Accordingly, an object of the present invention is to provide a liquid jetting device which is capable of reducing the number of required parts, eliminating the complicated control for the pressure regulation as needed by the related device, and reducing the cost to manufacture, and a liquid supplying method in use for the liquid jetting device.